Spark plug



Oct. l0, 1933. C. Q ERNY 1,930,003

SPARK PLUG Filed March 6, 1933 Patented Oct. 10, 1933 .UNITED STATES PATENT QFFCE Application March 6, 1933.

8 Claims.

This invention relates to improvements in spark plugs for internal combustion engines and the like, and the principal object oi" the invention is to provide a spark plug having generally improved structural and operating characteristics.

Another object of the invention is to provide a spark plug of simple and inexpensive construction capable of eiicient and durable operation in aeronautical motors.

More specifically, an object of the invention is to provide a spark plug wherein provision is made by novel means for preventing exposure of the spark terminals and of the insulator to excessively high temperature conditions.

Still another and specific object of the invention is to provide novel means for protecting the terminals and the insulator from carbon or other accumulations tending to decrease the eiciency of operation.

Still another and specic object of the invention is to provide a spark plug having the aforesaid protective means wherein provision is made for eectively Ventilating the interior or firing chamber of the spark plug to thereby prevent accumulations of spent gases and carbon-forming elements within the ring chamber.

Still another object of the invention is to provide novel and improved means for sealing the joints between the shell or casing of the spark plug and the insulator.

A still further object of the invention is to provide means for preventing access to the working parts oi the plug of oil or other foreign substances and to insure an adequate drainage from the firing chamber of the spark plug.

The invention further resides in certain novel structural features and details of construction hereinafter set forth and illustrated in the attached drawing, in which:

Figure 1 is a longitudinal sectional view of a plug made in accordance with my invention;

Fig. 2 is an inverted plan view of the plug;

Fig. 3 is a section on the line 3-3, Fig. 1, and

Figs. 4 and 5 are enlarged sectional views of the gaskets constituting the sealing means between the insulator and the shell or casing of the spark plug.

For aviation purposes, it has been found impractical to use the standard iorms of spark plug employed in the automotive industry due to the fact that the porcelain insulators commonly used in these plugs as well as the spark terminals are incapable of withstanding the excessively high temperatures to which they are subjected in the aeronautical motors. As a consequence, it has Serial No. 659,883

been necessary heretofore to employ in aeronautical engines specially designed spark plugs in which the insulator is of mica. Since frequent replacements are necessary, spark plugs represent a considerable item of expense in the air industry.

It is a purpose of the present invention to provide a plug of relatively simple and inexpensive capable of efficient operation in aeronautical engines, thereby to eilect a considerable economy in that industry. Plugs made in accordance with my invention, however, have proved themselves to constitute a material improvement over the present standard plugs in the automobile eld, are relativey efficient in operation, and efect a material economy in gas consumption. The plugs are also relatively durable and capable of giving satisfactory service over protracted periods of use.

In the attached drawing and with reference to Fig. 1, it will be noted that the spark plug comprises the usual metallic shell or casing 1 in which is installed an insulator 2, which may be oi porcelain or oi any other suitable material, this insulator being clamped in the casing 1 by 8O means of a gland 3 which embraces the upper portion of the insulator and is threaded into the shell 1. As illustrated, the insulator 2 has a portion 4 intermediate its ends of increased diameter, this enlarged portion providing a shoulder 5 which 85 engages a corresponding but reverse shoulder 6 in the shell l, to thereby fix the position of the insulator in the shell. At the opposite side of the enlarged portion 4, the shoulder 7 is opposed by the inner end of the gland 3 which clamps the insula- 90 tor in the shell. As clearly illustrated, the shoulder 5has acircumferential rib 8Which enters a peripheral recess in a gasket 9, see Figs. 1 and 5 wherein the gasket recess is designated by the reference numeral ll. This gasket has on its under side a protruding circumferential rib 12 which enters a corresponding recess 13 in the shoulder 6 of the shell 1. A gasket 14, see Figs. 1 and 4, is interposed between the inner end of theL gland 3 and the shoulder 7, this gasket 14 being tapered as illustrated whereby when the gland 3 is threaded down upon the gasket, the latter has a tendency to spread transversely against the surrounding walls ci the shell 1. Pressure thus exerted by the gland 3 is also transmitted to the gasket 9 which is placed under compression, and this pressure in conjunction with the inner engaging ribs and recesses o the gasket, the shell 1 and the insulator 2, effects a positive seal preventing any possible leakage between the shell and the insulator.

In accordance with the usual practice, the insulator 2 supports one of the terminal elements 15 of the spark plug, this element projecting from both ends of the electrode. As shown in Fig. 1, the inner end of the terminal element 15 projects into a chamber 16 in the interior of the shell 1 and into proximity to a terminal element 17 threaded into the lower closed end of the shell 1 and held in adjusted position therein by means of a lock screw 18. The chamber 16 constitutes in effect the firing chamber of the spark plug and is closed with the exception of a series of ports hereinafter described.

It will be noted that the lower outer edge of the shell 1 is beveled as shown at 19, and inthis beveled surface I provide in the present instance four ports 21 which extend inwardly to the chamber 16. As shown in llig. 3, the inner ends of these ports 21 enter the chamber on the junction line between the side walls 22 of the chamber 16 and the inclined bottom Wall 2S. This junction line is indicated in Fig. l by the refer ence numeral 2li. As illustrated in Fig. 1, the bottom of the chamber 1S is of frusto-conical form, the surface extending upwardly from the line 2li and terminating at the apex in the sides of the terminal element i'. Also as illustrated in Figs. 1, 2 and 3, the ports 21 are so formed that their longitudinal axes are remote to the terminals 15 and 17, so that any oil projected into the outer end of these ports, even along the axial lines of the latter, will not normally come in contact with the terminal elements but will strike the side wall of the chamber 16 and Will eventually now to the bottom of the chamber to be drawn or to flow by gravity from the ports 21. The inclined bottom wall of the chamber 16 precludes this oil from flowing into contact with the terminal 1'7. Similarly, the inner end of the insulator 2 is protected from possible contact by oil or other substance projected by'movement of the piston into contact with the spark plug.

Intersecting the beveled surface 19 is a port 25, this port as shown in Fig. l extending diagonally upwardly through the shell 1 and entering the chamber 16 at a point adjacent the top thereof. In the present instance I have shown a corresponding port, also designated by the reference numeral 25, at the opposite side of the shell. These ports preferably are of smaller diameter than the ports 21 previously described. I have found that a port of this character has a marked eiect in maintaining the inside of the chamber l5 free from carbon deposits, and a spark plug made as described above will maintain itself substantially free from carbon deposits in the ring chamber 16 over extended periods of use. This is probably due to the Ventilating effects of the ports 25, which apparently function to free the chamber 16 of spent or partially consumed vapors, and with the ports 21 maintain the gas content of the chamber 16 substantially free of the carbon-forming elements.

The various structural elements of the spark plug, including the substantially closed ring chamber 16; the ports 21 located to afford free access to the firing chamber of the fresh gases while preventing contact of oil with the spark plug terminals and with the insulator; the arrangement of these ports in conjunction with the conical bottom wall of the ring chamber which affords the self-draining characteristics; the Ventilating ports 25 which prevent the formation of a dead gas pocket at the top of the chamber and which are in large part responsible for the practically complete absence of any tendency to carbon formations within the firing chamber; and the gaskets 9 and 14 which are so formed as to entirely seal the upper end of the firing chamber against any possible leakage, all contribute to the production of a spark plug of high efficiency and ability to stand up under the most extreme conditions over long periods of time without loss in efficiency and without damage to the terminals or to the insulator due to excessive temperatures. reason of these characteristics, the plug is well adapted for use in aeronautical engines, and provides an entirely reliable spark plug for that purpose at a considerably lower cost than the spark plugs now commonly employed.

It will be apparent, of course, that there may be modifications in the structural details of the plug herein described without departure from the invention.

I claim:

1. A spark plug comprising a casing, and means for installing said casing in the cylinder wall of an internal combustion engine with one end exposed in the cylinder, said casing having in the interior thereof an enclosed firing chamber, and having in the exposed end thereof a plurality of ports, two of which ports enter the firing chamber at opposite ends thereof respectively.

2. A spark plug comprising a casing, a ring chamber enclosed within said casing, a firing port `extending from one end of said chamber to the outer` surface of the casing, and a Ventilating port extending from the'opposite end of said chamber to a point on the outer surface of said casing adjacent the firing port.

3. A spark plug comprising a casing having a firing chamber in one end, the bottom wall of said firing chamber being of substantially conical form, said casing having therein a plurality of ports communicating with said chamber at the line of junction between said bottom and the adjoining side walls, and spark terminals projecting into said chamber, said ports being so relatively arranged with respect to said terminals that the longitudinal axes of said ports extend in a direction remote to said terminals.

4. A spark plug comprising a casing cylindrical at one end and having in said cylindrical end a completely enclosed firing chamber, the edge of said cylindrical end portion of the casing being roo beveled, a plurality of ports extending from said beveled surface inwardly to the ring chamber, one of said ports communicating with the adjoining end of said chamber, and another of said ports extending through the casing to a point adjacent the other end of said chamber.

5. In a spark plug, the combination with a metallic casing having an interior recess extending from one end to a point adjacent the opposite end, said last-named end of the casing being cylindrical and being externally threaded whereby the casing can be secured in the cylinder Wall of an internal combustion engine, an insulator projecting into said casing recess from the open end thereof and terminating short of the bottom of said recess to provide an enclosed firing chainber, oppositely arranged shoulders in the wall of said recess and on said insulator determining the position of said insulator in the casing, a second shoulder on said insulator, an element threaded into said casing and engaging said second shoulder to hold the insulator in the casing,

gaskets interposed between the `opposed casing and insulator shoulders and between the said second shoulder of the insulator and said retaining element, at least one of said gaskets and the surfaces engaged thereby having complementary and interengaging ribs and recesses to thereby effect a complete seal between the insulator and the casing, a terminal element extending longitudinally of said insulator and projecting into the said firing chamber, the end wall of said chamber being frusto-conical in form and having a threaded port intersecting the apex end of said cone and extending to the outer surface of said casing, a terminal element threaded into said port and extending to a point adjacent the end of the JFirst-named terminal, means for locking the threaded terminal in its port, the cylindrical end of said casing having its edge portions beveled and having ports extending from said beveled surfaces inwardly to said chamber and intersecting the Wall of said chamber at the line of junction between the said conical end and side walls, and a port extending from said beveled surface to a point adjacent the opposite end of said chamber and providing for Ventilation of said chamber.

6. A spark plug having at one end an enclosed firing chamber, the outer Wall of said chamber being screw-threaded intermediate its ends to permit installation of said plug, and said chamber having ports both at its inner and outer ends extending froin the interior to the exterior of said plug, all of said ports terminating at points on the chambered end located in a common plane transverse to the plug and outwardly of the threaded section.

7. A spark plug having an enclosed firing chamber at one end, firing ports at the outer end of said chamber, and channels extending longitudinally of said plug through the side Walls of said chamber from points on the outer surface of the plug adjacent said ring ports and terminating in the inner Wall of said chamber adjacent the inner end of the latter.

8. A spark plug having a firing chamber at one end and a channel extending through the side walls of said ring chamber from the interior to the exterior thereof and from a point adjacent the inner end of said chamber to a point adjacent the outer end of said chamber.

CHARLES G. ERNY. 

